In electronic devices of recent years, there is a tendency of lighter weighted, thinner thickness, shorter length and smaller size, but there is a problem on securing a high output and a small power source. To solve the problem, attempt has been made to lower the power consumption and to elongate the lifetime of a secondary battery of each of various devices that constitute the electronic device.
The best example of the electronic device of lighter weighted, thinner thickness, shorter length and smaller size is a portable electronic watch. The portable electronic watch has smaller power consumption and smaller size as compared with a mobile phone which has remarkably been developed in recent years. Therefore, even when a primary battery such as a button type lithium battery is used as an embedded power source, changing frequency is once in several years, which is sufficiently practical. However, for users, it is troublesome to change battery even once in several years, and it requires costs. Even when a secondary battery is used as the embedded battery, it is troublesome to charge the battery. Especially with the electronic watch, it is necessary to reset the time after the battery is changed, and therefore it is not preferable to repeatedly inflict such operation on users.
Thereupon, an electronic watch in which an electricity generating device that generates electricity to be stored in the secondary battery is embedded together with the secondary battery, has been commercialized. A solar cell which converts optical energy to electricity, a thermionic element which converts energy due to a temperature difference between body heat and outside air temperature into electricity, a rotating weight which converts kinetic energy into electricity, or the like is used as the electricity generating device.
Not only a digital display type electronic watch using a liquid crystal but also an analogue display type electronic watch using hands in many cases includes an IC chip which generates a reference clock or controls a motor which rotates the hands. The electricity generated by the electricity generating device is consumed as driving voltage of the IC chip or the motor through the secondary battery.
Therefore, in the electronic watch having the electricity generating device, it is important that the electricity generating device is excellent in order to keep the stable watch operation, and the operation is carefully confirmed during producing procedure also.
Especially, the electronic watch is small in size, and therefore the operation of the electricity generating device alone is usually checked first in pre-step in which constituent parts of the electronic watch are incorporated. Subsequently, the electricity generating device which was confirmed as a fair quality is incorporated into the electronic watch and the operation of the electronic watch is confirmed.
However, electricity to some extent is stored in the secondary battery which is incorporated together with the electricity generating device. Therefore, an electronic watch which is operated using the electricity stored in the secondary battery sometimes shows normal watch operation immediately after the incorporation, even when the electricity generating device is damaged during incorporation. The damage of the electricity generating device mentioned here includes damage of the electricity generating device itself caused by generation of static electricity during the incorporation, and also includes such when electric wiring between the electricity generating device and the secondary battery is disconnected and the electricity generating operation of the electricity generating device can not be confirmed visually.
In an electronic watch which was shipped as being a normal watch for the above reason, the stored electricity of the secondary battery runs out after a while, and the watch operation is stopped.
Thus, after the electronic watch was assembled, i.e., in a product form immediately before shipment, an electricity generating device capable of confirming the operation has been required.
It is an object of the present invention to provide an electronic watch capable of easily confirming the operation of a built-in electricity generating device in a product form.